02 julio 2014

Scientists have found the first evidence of a physical mechanism that may stop us from remembering our early childhood.

Image: StudioSmart

Researchers have long puzzled over why we can form memories when
we’re babies, but then go on to have no recollection of those years - a
phenomenon known as infantile amnesia.
Now recent research in rodents may have found the answer. It turns
out all the new cells that are constantly being formed in young brains
may actually be messing with our memories.
Mammals generate new brain cells all the time, but when we’re babies
the rate of this process, known as neurogenesis, is at its highest.
Because of all the new things we experience as infants, there’s a lot of
early-life action in the hippocampus in particular - the region of the
brain that is associated with memories and learning.
Usually this type of hippocampus activity is associated with improved memory, as Susannah Locke writes for Vox.
But a study led by scientists from the University of Toronto in Canada
has found that in babies, the extremely high rates of neurogenesis is
actually having the opposite effect and increasing forgetfulness.
Their research, published in Science, suggests that all the new neurons being formed could be pushing out established memory circuits.
The team investigated the process by first creating memories in
various rodents. To do this they made the animals associate a place with
a mild electric shock.
They then boosted the rate of neurogenesis in some of the mice by
either giving them drugs or a running wheel (both known to stimulate
neuron production in the rodents), and slowed down neurogenesis in
others.They found that the young mice who’d had their neuron production
slowed down were able to remember things better than those that had the
process sped up.
The researchers also looked at guinea pigs and a Chilean rodent
called a degu, two species which are born with a more mature brain and
have naturally lower rates of neurogensis when they’re infants. Neither
of these species normally experience infantile amnesia, but when the
scientists increased their rates of neurogenesis above normal levels,
neither could store memories from when they were babies.
Given the similarities between rodent and human brains, the
researchers believe the same process could cause humans to forget their
early childhood.Previous theories have suggested that infantile amnesia comes from babies’ lack of language skills or emotional development,as Locke explains in Vox.
This new research doesn’t necessarily rule out the ideas, but shows for
the first time the mechanism through which our memories are
suppressed.Mazen Kheirbek, a neuroscientist from Columbia University in the US told Vox
that further research is needed to work out whether it’s the new
neurons that are leading to forgetting, or the learning itself. "Perhaps
the forgetting seen here is actually due to the increased ability to
learn new things," he said."So there is a tradeoff there, preserving the older memories may come at the cost of making new ones."
And just in case anyone was wondering, this is what a degu looks like (adorable):